Antibacterial activity of 13 condiments used in Thai cooking was investigated with a pandemic strain of Vibrio parahaemolyticus.
Using a disk diffusion technique, freshly squeezed extracts from galangal, garlic and lemon, at a concentration of 10 ml/disk produced a
clear zone of 13.670.5, 11.670.5 and 8.671.2 mm, respectively. The inhibitory activity of these 3 condiments on pandemic strains was
not significantly different from that on non-pandemic strains of V. parahaemolyticus. Because of its popularity in seafood cooking,
galangal was subjected to further investigation. Only a chloroform extract of galangal inhibited growth of V. parahaemolyticus producing
a clear zone of 9.570.5, 12.070 and 13.570.5mm diameter at concentrations of 25, 50 and 100 mg/disk, respectively. One active
component is identified as 10-acetoxychavicol acetate. The activity of galangal was not reduced at pH 3 or in the presence of 0.15% bile
salt but was reduced by freeze and spray drying. Heating a fresh preparation of galangal to 100 1C but not 50 1C for 30 min also reduced
growth inhibition. Therefore, using fresh galangal in cooking was recommended. The MIC and MBC of a freshly squeezed preparation
of galangal were 1:16 and 1:16, respectively. This is the first report of an inhibitory activity of a Thai medicinal plant, galangal that is
used in Thai cooking, on the pandemic strain of V. parahaemolyticus.
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